GB2466640A

GB2466640A - Safety pin arrangement for a multi-hitch

Info

Publication number: GB2466640A
Application number: GB0823639A
Authority: GB
Inventors: Anthony Joseph Bianchi
Original assignee: QUICK SWITCH
Current assignee: QUICK SWITCH
Priority date: 2008-12-31
Filing date: 2008-12-31
Publication date: 2010-07-07
Also published as: GB0823639D0

Abstract

A safety pin arrangement 50 for a multi-hitch 10 of a mechanical arm comprises a first pin 52 having a first length and a second dummy pin 54 having a second length shorter than the first length. The pins 52, 54 are connected together by a plate 56, which holds the pins 52, 54 parallel to one another in spaced relationship. The arrangement can be inserted in a pair of adjacent safety holes on a multi-hitch 10, the longer pin 52 locking the mechanism. Both the pin 52 and pin 54 are capable of being detected by a sensor allowing a single sensor to monitor three safety pin apertures by positioning the shorter pin 54 in the aperture with the sensor when the longer pin 52 is locking the mechanism by being positioned in an adjacent aperture.

Description

Safety Pin Arrangement for a Multi-hitch The present invention relates to a safety pin arrangement for a multi-hitch and particularly to a safety pin arrangement for a multi-hitch of a mechanical arm, for example, an excavator arm.

An excavator arm typically includes a boom, a dipper arm and a bucket, all powered by hydraulic rams. In use, an excavator operator may have to change a bucket or other tool attachment a number of times per day in order to optimise the productivity of the machine. In some cases, an operator may change a bucket on an excavator up to thirty times per day.

Most excavators are fitted with a quick hitch or coupler in order to speed up the process of changing a bucket. A standard bucket is usually attached to the end of the dipper arm using two spaced and parallel pins. A quick hitch is a system in which one of the pins is generally located in an open-mouthed substantially C-shaped aperture and the other pin is located in a similar C-shaped aperture, but is secured within the aperture by means of a movable jaw or catch. The C-shaped apertures are arranged such that when the first pin is located in the first aperture and the second pin is secured in the second aperture and the jaw closed, the bucket is securely held to the quick hitch.

In other arrangements, custom made pins, apertures and lugs may be provided to secure a bucket or other tool, but the principal of holding the bucket or tool to the quick hitch is the same, in that a movable jaw or catch secures a pin of the bucket or tool to the dipper arm.

Some quick hitch systems are operated manually, but the majority of quick hitches are semi-automatic or fully automatic. A manual arrangement requires an operator to open and close the jaw manually, or to open a spring operated latch using a lever.

This involves the operator leaving the excavator cab and is relatively slow and inconvenient.

A semi-automatic quick hitch generally includes a movable jaw, which is powered by a hydraulic ram. The ram can be operated from the cab of the excavator, but because the system relies on the hydraulics of the machine, a safety pin is inserted by hand, which locks the movable jaw in its closed position. The safety pin is also known as a "safety bar" and prevents the jaw from opening in the event of a hydraulic failure or operator error.

A fully automatic quick hitch is operated entirely from within the excavator cab and utilises a movable hydraulic jaw similar to that in a semi-automatic arrangement.

However, an independent locking system for the hydraulic jaw is usually provided, which does not rely on hydraulic pressure. Furthermore, a visible indicator may be provided on the quick hitch, which indicates when the bucket or tool is secure. In one arrangement, a locking pin may protrude from the side of the quick hitch if it is not in a securely locked condition. The protruding pin can be seen from the cab of the excavator by the operator and serves as a warning that the bucket or other tool is not secure.

A multi-hitch, also known as a multi-pin grab (MPG) is a quick hitch, which can he connected to attachments with different pin centres. A reason for using a multi-hitch is that different manufacturers of attachments use different pin centres. A plant company may have a mixed fleet of attachments that can only be connected or picked up by a single hitch if it is a multi-hitch. Due to the variation in pin centres, the movable jaw does not come to rest in the same position when attaching tools with different pin centres and therefore the optimum position for insertion of the safety pin, immediately adjacent the jaw to block its path, changes. The safety pin on a multi-hitch is therefore positioned in one of a number of possible apertures in the body of the hitch, depending on the distance that the movable jaw moves. Typically there are 3 holes, the central axes of which are spaced apart.

It is an acknowledged problem of semi-automatic or fully automatic quick hitch arrangements that if the hydraulic jaw holding the bucket or tool accidentally retracts due to operator error or hydraulic failure, then the bucket or tool will fall from the dipper arm potentially causing a serious accident. In the last year approximately 13% of investigated excavator incidents in the UK have been caused by an excavator bucket detaching unexpectedly from a quick hitch and injuring or killing a ground worker. In the last year five ground workers have been killed due to the accidental release of a bucket from a semi-automatic quick hitch.

A reason for a semi-automatic quick hitch failing is the omission of an excavator operative to fit the safety pin. Reasons for this omission include the desire to speed up the changing of buckets, reluctance to insert the pin in bad weather because it is necessary to leave the excavator cab, or a misplaced pin. An operative may also incorrectly fit a safety pin. The applicant's co-pending application GB 0725354.5, proposes a safety device for a quick hitch including a sensor for detecting the absence of a safety pin and to sound an alarm if the pin is not detected. However, on a multi-hitch, the problem arises of where to mount the sensor, because there are usually three safety pin apertures, any one of which could be in use, or not.

According to a first aspect of the present invention there is provided a safety pin arrangement for a multi-hitch of a mechanical arm comprising a first pin having a first length, a second pin having a second length shorter than the first length, and connection means, the connection means being connected to one end of each of the respective first and second pins and holding the first and second pins parallel to one another in spaced relationship.

It is an advantage of the invention that when the first pin of the safety pin arrangement is located in an appropriate safety pin aperture, the second pin is located in an adjacent aperture. This means that only one sensor need be provided for both apertures. The second pin is effectively a "dummy" pin, which does not act to prevent movement of a hydraulic arm of a hitch, but rather serves to indicate the presence of another adjacent safety pin. When the first pin is located in the aperture where the sensor is located, the dummy pin serves no purpose.

Preferably the second length is less than half of the length of the first length.

Advantageously the length of the second pin is long enough to he identified by the sensor, but is short enough to be clear of the movable jaw or locking arm.

Preferably the connection means is a substantially flat plate and the first and second pins extend perpendicularly therefrom.

Preferably the distance between central axes of the first and second pins is adjustable.

One of the first and second pins may be fixed relative to the plate and the other of the pins may be movable relative to the plate.

Preferably the first pin is fixed relative to the plate and the second pin is movable relative to the plate.

Preferably an elongate slot is provided in the plate and the second pin is adjustably mounted to the plate through the elongate slot.

Preferably the first pin has a portion of reduced diameter partway along its length.

The diameter of the portion of reduced diameter may be reduced by around 2 mm.

According to a second aspect of the present invention there is provided a multi-hitch comprising at least one hydraulically actuated arm for engaging a pin of a tool, at least two safety pin apertures provided in the body portion of the multi-hitch, a safety pin arrangement according to the first aspect of the invention for locking the at least one hydraulically actuated arm in an engaged position in one of at least two positions, a sensor for detecting the presence or absence of the safety pin arrangement in the engaged position and an alarm means connected to the sensor for indicating when an absence of the safety pin is detected.

Preferably three safety pin apertures are provided in the body portion of the multi-hitch.

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a schematic side view of a multi-hitch arrangement; Figure 2 shows a cross-sectional view through a safety pin arrangement of the invention: Figure 3A shows a schematic plan view of a plate and first safety pin; and Figure 313 shows a schematic exploded view of the second pin assembly.

Referring firstly to Figure 1, a quick hitch is indicated generally at 10. The quick hitch 10 is also a multi-hitch as previously described and is pivotally mounted on one side to the distal end of a dipper arm 12 of an excavator about a pivot 14. The other side of the quick hitch 10 is pivotally mounted to a connecting arm 20 about a pivot 22, which is itself pivotally connected to a hydraulic ram. The hydraulic ram controls the movement of a bucket or other tool connected to the quick hitch 10.

The quick hitch 10 includes a body portion 24 including a first open-mouthed substantially C-shaped aperture 26 facing in one direction, ie to the left of the drawing as viewed, and a second open mouthed substantially C-shaped aperture 28 facing the bottom of the page, as viewed. In other words, the mouths of the apertures 26, 28 are substantially perpendicularly disposed relative to one-another. A movable jaw 30, shown partly in dotted outline, pivots about a pivot point 31 between a closed position, as viewed, in which the hooked tip 16 of the jaw 30 closes over the mouth of the aperture 28 and an open position (not shown) in which the jaw 30 is rotated away from the aperture 28, allowing the aperture to receive a pin of an excavator bucket or other tool. The jaw is powered by a hydraulic ram 32, shown in dotted outline.

Three apertures 34, 36, 38 are provided through the body portion 24 of the quick-hitch for receiving a safety pin as described in further detail below for locking the jaw 30 in a closed position. The jaw 30 is opened and closed by means of the hydraulic ram 32 and comes to rest in different positions depending on the distance between the attachment pins of a tool. For example, one pin of the tool is located in the base of the aperture 26, but the other pin may he positioned at any lateral position in the base of the aperture 28, depending on the pin centres of the tool. Apertures are also provided through the jaw 30 for receiving the safety pin and the apertures align with at least one of the respective apertures, 34. 36, 38 depending on where the jaw comes to rest.

For example, as shown in Figure 1, the safety pin should be positioned in the first aperture 34 to most effectively prevent opening movement of the jaw 30. In other arrangements, the jaw 30 may not be apertured, but the safety pin may bear against the back of the jaw to prevent the jaw from opening. In some arrangements, the jaw extends above the pivot 31 and in this case, the safety pin may bear against the front of the jaw above the pivot 31 to prevent the jaw from opening, ie in a clockwise direction about the pivot 31, as viewed.

A sensor 40, for example a proximity switch, is mounted on a bracket 42 and is positioned to detect the presence or absence of a safety pin or safety bar in the aperture 36. The proximity switch can be a micro-switch, an inductive or a magnetic switch or any other switch type capable of detecting the presence or absence of the safety pin. When the safety pin is located in the aperture 36, it blocks the path of the jaw 30, which is prevented from opening.

Referring to Figure 2, a safety pin arrangement is indicated at 50. The safety pin arrangement 50 includes a first safety pin 52 and a second dummy pin 54. The pins 52, 54 are mounted to a connecting plate 56 and are arranged spaced apart and parallel with one another. The pins 52,54 are the same diameter, but the second pin 54 is shorter than the first pin 52. This enables it to he inserted in one of the apertures 34, 36, 38 and not impede movement of the jaw 30. The first pin has a portion of reduced diameter 51, part-way along the pin 52, and substantially beginning at the position where the second pin terminates. An aperture 53 is also provided through the diameter of the pin 52 at its end, for receiving a spring clip or split pin. The first pin 52 is permanently attached to the plate for example by welding and the second pin is adjustably mounted to the plate 56 by means of a locking cap 58 and cap screw 60.

Referring also to Figures 3A and 3B, an elongate aperture 62 is provided through the plate, the longitudinal axis of the aperture 62 being aligned with the central axis of the pin 52.

A threaded bore 64 is provided in one end of the second pin 54 which is adapted to receive the threaded cap screw 60. The locking cap 58 is apertured to receive the head and shaft of the cap screw 60 and has a portion 68 of large diameter and a stepped down portion 70 of reduced diameter, which is adapted to slide in the elongate slot 62 of the plate 56. When assembled, as shown in Figure 2, the pin 54 sits on one side of the plate, the same side as the pin 52, and the locking cap 58 and cap screw 60 secure the pin 54 to the plate 56 from the other side. When tightened, the cap screw 60 does not rigidly connect the locking cap 58 and the pin 54 to the plate 56, but the locking cap 58 is able to slide freely within the elongate slot 62. In other words, the tolerance between the locking cap 58 and elongate slot is tight enough to hold the pin 54 securely to the plate 56, but loose enough to allow adjustment of the position of the pin 54.

In use, when a bucket or other tool is secured to the quick hitch 10 and the jaw 30 is closed, the pins 52, 54 of the safety pin arrangement 50 are inserted in two adjacent apertures of the hitch. The pin 52 is inserted in the appropriate aperture to prevent undesired movement of the jaw 30 and at least one of the pins 52, 54 enters the central aperture 36 of the hitch body 24, and thus is detected by the sensor 42. In this condition, safe operation of the excavator can resume. If for some reason, the pins should start to move back out of their respective apertures, then when the step down in diameter of the pin 52 to the reduced diameter portion 51 moves past the sensor, this change in diameter is detected and the machine alarm sounds. This warns the operator to stop operating the machine and check the location of the safety pin arrangement 50.

The size of the pins 52, 54 and the distance between the apertures 34, 36 and 38 depends on the size of the multi-hitch. In a typical example for use on an excavator, the first pin 52 is between 400mm and 500mm long and the second dummy pin is between 120mm and 150mm long. The diameter of the pins is typically between 20mm and 70mm. The space between the peripheries of the first and second apertures 34, 36 is typically around 9mm and the space between the peripheries of the second and third apertures 36, 38 is typically around 1 3niiri. Therefore in this example, adjustment of at least 4mm is required on the plate 56.

In use, if neither the first pin 52 nor the second pin 54 is detected by the sensor 42, then an alarm is activated. In this condition, operation of the excavator is unsafe and the operator is warned that a safety pin should be inserted.

It is envisaged that use of the safety pin arrangement 50 will substantially reduce or even eradicate accidents caused by operator error and hydraulic failure with multi-hitches. The arrangement 50 provides for the use of a single sensor to monitor the presence or absence of a safety pin in three separate apertures.

Claims

CLAIMS1. A safety pin arrangement for a multi-hitch of a mechanical arm comprising a first pin having a first length, a second pin having a second length shorter than the first length, and connection means, the connection means being connected to one end of each of the respective first and second pins and holding the first and second pins parallel to one another in spaced relationship.
2. A safety pin arrangement as claimed in claim 1, in which the second length is less than half of the length of the first length.
3. A safety pin arrangement as claimed in claim 1 or claim 2, in which the connection means is a substantially flat plate and the first and second pins extend perpendicularly therefrom.
4. A safety pin arrangement as claimed in claim 3, in which the distance between central axes of the first and second pins is adjustable.
5. A safety pin arrangement as claimed in claim 4, in which one of the first and second pins is fixed relative to the plate and the other of the pins is movable relative to the plate.
6. A safety pin arrangement as claimed in claim 5, in which the fist pin is fixed relative to the plate and the second pin is movable relative to the plate.
7. A safety device as claimed in claim 6, in which an elongate slot is provided in the plate and the second pin is adjustably mounted to the plate through the elongate slot.
8. A safety device as claimed in any preceding claim, in which the first pin has a portion of reduced diameter partway along its length.
9. A safety device as claimed in claim 8, in which the diameter of the reduced diameter portion is reduced by around 2mm.
10. A multi-hitch comprising at least one hydraulically actuated arm for engaging a pin of a tool, at least two safety pin apertures provided in the body portion of the multi-hitch in different positions, a safety pin arrangement as claimed in any one of claims 1 to 9 for locking the at least one hydraulically actuated arm in an engaged position in one of at least two positions, a sensor for detecting the presence or absence of the safety pin arrangement in the engaged position and an alarm means connected to the sensor for indicating when an absence of the safety pin arrangement is detected.
11. A multi-hitch as claimed in claim 10, in which three safety pin apertures are provided in the body portion of the multi-hitch.
12. A safety device substantially as claimed herein with reference to and as illustrated in Figures 1 to 38 of the accompanying drawings.